Lance carriage

ABSTRACT

An elongate lance (4) is raised or lowered by means of a carnage (7) which is guided by vertical channels (8). The lance has lateral projections (18) whereby it is supported in a cradle (17) mounted to carriage (7) via springs (29). The apparatus permits the lance lower end (12) to be submerged in bath (3) and permits restricted lateral movement of the lance lower end.

TECHNICAL FIELD

The present invention relates to furnaces and in particular to apparatusto inject material into a furnace bath.

BACKGROUND OF THE INVENTION

It is conventional to inject materials such as air into furnace bathsvia openings (or tuyers) located towards the bottom of the furnace. Itis also known in steel making to direct oxygen into a furnace viaaxially mounted downwardly extending lances suspended above the bath.More recently it has been proposed to use a pyrometallurgical lancewhich can be lowered into the furnace bath from above. In such proposalsthe lances inject air or oxygen enriched air through an outer tube andin some processes, a fuel such as oil or coal through a concentric innertube. Swirlers are located the lance to improve cooling of the outerwall. As the the lower end or tip of the lance is lowered into thefurnace, slag resting on the top of the bath may splash on to the lanceand freeze and adds further protection as the lance contacts with thebath.

Relatively small pilot plants having a capacity of 50 kg to 5000 kg havebeen described in which a lance of approximately 2-12 cm cross sectionis raised and lowered by a wire and pulley and stabilized by guy wires.However, such means would not be practical for a large scale plant witha lance of for example 30-45 cm diameter and being 10 meters long. Whenthe lance tip is submerged the bath becomes intensely agitated. Theselances require to be periodically repaired due to consumption of thelance tip. Problems have been encountered in trials involvingmaneuvering of such lances into and out of position as well as inraising and lowering the lance into the furnace. Because of the size andweight of the lance and space constraints typical of a furnace site,maneuvering a lance into and out of its mounting is intrinsicallydifficult and potentially hazardous. Replacement of one lance by anothermust be accomplished without delay. Moreover it has been discovered thatif a 10 meter long lance is rigidly mounted as hitherto practiced withnon submerged lances, stresses are introduced due to the intenseagitation of the melt at the lower end of the lance and the lancefractures or the carriage and guides is damaged.

It has also been found that if too great a latitude of movement of thelance tip is permitted, the lance deflects the circulating bath flowcausing increased wear on the lance itself, and introducing undesirablemixing of the bath. Furthermore, in situations of continuous feed and/orcontinuous or batch tapping it is necessary to control the height of thelance tip to ensure adequate oxygen transfer and temperature control ofthe bath.

It is an object of the present invention to provide improved means forraising and lowering a lance into a furnace.

SUMMARY OF THE INVENTION

According to one broad form the invention consists of an apparatus forinjecting material into a furnace bath comprising an elongate lancehaving a lance lower end, a carriage including lance mounting means forreleasably supporting the lance, means for guiding the carriage upwardlyand downwardly whereby to move the lance lower end between a positionabove the bath and a position submerged in the bath, and means to permitrestricted lateral movement of the lance lower end relative to thefurnace bath.

Preferably the carriage runs on guide columns above the furnace bath.

In a preferred embodiment the lance has laterally projecting shaftswhich are supported in a cradle on the carriage and the cradle isresiliently mounted to the carriage to allow a degree of lateralmovement of the lance with respect to the carriage and furnace bath.

The submerged tip of a lance mounted according to the invention is ableto move laterally through an arc of up to, but not greater than 10°(i.e. 5° from vertical), and more preferably through an arc of at least2.5° but not greater than 5° (i.e. not greater than 2.5° from vertical).

BRIEF DESCRIPTION OF DRAWINGS

A preferred embodiment of the invention will now be described, by way ofexample only, with reference to the accompanying drawings in which:

FIG. 1A is a schematic representation of a furnace arrangement showing alance in a lowered position. FIG. 1B corresponds to FIG. 1A but showsthe lance in a raised position;

FIG. 2 is a section view of a lance used with the present invention;

FIG. 3 is a schematic representation in elevation of a carriageaccording to the present invention;

FIG. 4 is a detailed elevation view of the carriage according to theinvention with the lance mounted thereto;

FIG. 5 is a plan view of the carriage and lance of FIG. 4;

FIG. 6 is a sectional side elevation of the apparatus of FIG. 4;

FIG. 7 is a side elevation of the apparatus of FIG. 4;

FIG. 8 is a detailed view of the side rollers of the carriage of FIGS. 4to 7;

FIG. 9 is a detailed view of the front roller of the carriage and thechain drive; and

FIG. 10 is a plan view of the internal sleeve of the carriage accordingto the invention; and

FIG. 11 is a detailed view of the lower chain connection.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring to the drawings a furnace arrangement is shown schematicallyin FIGS. 1A and 1B. Furnace 2 is an upright generally cylindricalfurnace containing a bath having a bath surface 3.

Typically, a furnace bath contains a layer of slag. A layer of liquidmetal or matte may underlie the slag.

The furnace arrangement of FIG. 1A includes a lance 4 which in FIG. 1Ais shown in a lowered position with the lance tip submerged below bathsurface and in FIG. 1B is shown in a raised position. Lance 4 isconnected via a flexible coupling 14 through a series of pipework 5 to asource of material, in this case air, which is to be injected into thefurnace bath. The arrangement is seen to include a framework 6 severalstories high (with reference to a man's silhouette) provided withplatforms for access to machinery. Lance 4 is typically about 10 meterslong. The top of lance 4 is releasably mounted on a carriage 7 whichwill be described in detail hereinafter, for reciprocal movement in avertical direction to the furnace 2. Carriage 7 runs on guide channels 8mounted to framework 6 and is raised and lowered on a chain 9 connectedto the top and bottom of carriage 7 as also discussed below. Chain 9 isdriven by runs over pulleys 10 at the top of the installation and isdriven by a motor 11. The chain returns via pulley 10 at the bottom ofthe illustration and is fastened to the bottom of the carriage to ensurepositive drive in both raise and lower directions. Overhead cranes (notillustrated) are used to lift lance 4 off carriage 7 for lancereplacement. During this operation the carriage is in the raisedposition.

The lower end 12 (or "lance tip") of lance 4 is shown in FIG. 2 andincludes a swirler 121 adjacent the tip to assist in the distribution ofmaterial into the furnace bath. Lance 4 includes an inner tube 122surrounded by an outer tube 123 which define an outlet at the lancelower end. In the present example, air is injected into the furnace baththrough outer tube 123 and oil through inner tube 122. The lance mayoptionally have a gooseneck at its upper end as shown in FIGS. 4 and 5or may be straight.

In use tip 12 of lance 4 is lowered to be immersed in the molten furnacebath at which time air or air and fuel in a predetermined ratio isinjected into the bath. Care needs to be taken to ensure that lance tip12 does not become immersed in the matte layer as permanent damage wouldthen be effected within a short time after immersion. If correctlypositioned within the bath, lance 4 can be used for extended periods.Furnace 2 may be run on a continual feed and batch tapping process whichrequires that the level of lance 4 is continuously controlled to avoidcontact with the matte layer or may be run on a batch or continuousbasis.

Apparatus 15 to raise and lower lance 4 within furnace 2 is seen inFIGS. 3 to 7. This apparatus includes carriage 7 having a rigid frame ofupright members 20 and cross members 21. Upright members 20 have rollerhousings 22 mounted at top and bottom for clamping of rollers 16 onaxles 23 at front and back. Side rollers 24 on axles 25 are mounted onan inner surface of housings 22 so that both rollers 16 and 24 run alongvertical guide channels 8.

A lance supporting cradle 17 is resiliently mounted to carriage 7 by wayof two channels 40 extending outwardly from both upright members 20. Thecradle comprises two vertically disposed side plates 26 a back plate 27and horizontally extending profiled plates 28. The cradle is mounted tothe carriage via three resilient mountings 29.

FIG. 4 depicts a front view of carriage 7 and lance 4, the arrangementof carriage 7 on guide channels 8 is clearly seen. Lance 4 is releasablysupported on cradle 17 of carriage 7 by two opposed laterally projectingshafts 18 protruding from sides of lance 4, which rest in respectiveslotted cradle plates 26. During mounting the lance is guided by profileplates 28. Shafts 18 are strengthened on the upper edge by angle bracket19. This arrangement allows pivotal movement of lance 4 during mounting.Lance 4 is, in use, clamped to carriage 7 to prevent accidentaldisengagement from cradle means 17 by means not illustrated. Thisclamping may be achieved for example by providing tabs on the lanceadapted for bolted coupling to the cradle to restrict the range ofpivoted movement. It is necessary that lance 4 is allowed apredetermined degree of movement at tip 12 due to the length of lance 4and the agitation induced within the bath. If lance 4 were to be heldrigidly in place this would result in fracture of the lance or damage tothe carriage. It is desirable that tip 12 is allowed to move 2.5° to 5°off centre in any direction. Thus a 10 meter lance might move 60centimeters from vertical at the tip, Any further movement could resultin undesirable mixing of the molten metal and slag causing uneven wearon both the refractory bricks and on the lance tip.

As previously described carriage 7 runs on guide channels 8 by way offront and back rollers 16 and side rollers 24, Profile plates 28 arewelded within cradle 17 and as seen in FIGS. 5 and 10, Profile plates 28have an arcuate rear surface of a similar curvature of lance 4 howeverwith a tolerance therebetween. Cradle 17 comprising: profile plates 28together with slotted cradle side plates 26 is resiliently attached tocarriage 7 by a plurality of resilient mounts 29 or compression springs.

A feed pipe 30 at the top of lance 4 projects through the outer wall andconnects with inner tube 122 to feed oil through lance 4. Flexiblecouplings are provided for connection of lance 4 to the air supply andlikewise for connection of the oil line 122 to an oil supply.

FIG. 6 is a sectioned side elevation which shows one shaft 18 on theside of lance 4. Side rollers 24 are clearly shown at the top and bottomof carriage 7 for guidance along guide channel 8. The side elevation ofFIG. 7 illustrates how shafts 18 fit within the cradle formed by slottedside plate 26. One set of resilient mounts 29 is seen connecting cradleplates 26 to carriage 7 and a further one is shown offset behind column8.

A detailed view of roller housing 22 showing a pair of side rollers 24is depicted in FIG. 8 together with clamping block 31 on either side.Rollers 24 run symmetrically on channel 8 guiding carriage 7 axially upand down the furnace. Housing 22 includes an array of plates and anglesbolted together to partially encompass guide channels 8.

Referring to FIG. 1A and 1B it can be seen that lance 4 is moved up anddown with carriage 7 by way of a chain 9 and pulley 10 arrangement.FIGS. 9 and 11 show the connection of the chain, firstly to the top ofcarriage 7 at shackle 32 on cross member 21 and also at one side at thebottom of carriage 7 and on housing 22 at location 33.

In use lance 4 is raised and lowered into furnace 2 when chain 9 isoperated over pulleys 10. This controls the movement of carriage 7 alongguide columns 8 which restricts movement in directions other thanvertical. Lance 4 is also allowed to move through a predetermined angleat tip 12 due to cradle means 17 and the resilient mountings 29 ofcradle 17 with respect to on carriage 7. An operator can readily controlthe depth of immersion of lance 4 within the molten slag to avoidcontact with the matte layer.

Whereas air and oil have been disclosed for use with of the lance, othersubstances for example coal may be injected via suitably designedlances. It is also envisaged that other drive means may be employed toraise and lower the lance, for example, a rack and pinion, or cable orthe like.

It is highly preferred that the lance be coupled to supply ducting via ahigh temperature bellows 14 for example of cloth and a rubber whichaccommodates the motion of the lance. Duct 5 is provided with swiveljoints to accommodate gross lance movement.

The lance may be coupled to supply systems by other flexible meansand/or the ducting may be provided with valves and disconnected when thelance is raised.

Although the invention has been described with reference to specificexamples, it will be appreciated by those skilled in the art that theinvention may be embodied in other forms without departing from thescope hereof.

I claim:
 1. Apparatus for injecting material below the surface of afurnace bath comprising an elongate lance having a lance lower end witha lateral projection, a carriage including lance mounting meansresiliently connected to the carriage to permit restricting lateralmovement of the lance lower end relative to the furnace bath whereinsaid lance mounting means comprises a cradle for receiving said lateralprojection, means for guiding the carriage upwardly and downwardlywhereby to move the lance lower end between a position above the bathand a position submerged in the bath, and means to permit restrictedlateral movement of the lance lower end relative to the furnace bath. 2.Apparatus according to claim 1 wherein the means for guiding thecarriage upwardly and downwardly comprises at least one guide columnextending above the furnace.
 3. Apparatus according to claim 1 whereinthe lance mounting means is resiliently connected to the carriage bymeans including a plurality of compression springs.
 4. Apparatusaccording to claim 1 wherein the lance lower end is free to move throughan angle of up to but not more than 5.0° from vertical.
 5. Apparatusaccording to claim 1 wherein the lance lower end is free to move throughan angle of up to but not more than 2.5° from vertical.
 6. A method ofinjecting material below an upper surface of a bath in a furnacecomprising the steps of:releasably supporting an elongate lance on acarriage, guiding the carriage upwardly or downwardly so as to move thelance between a raised position in which a lower lance end is above thebath, and a lower position in which the lower lance end is submerged inthe bath, and permitting the lower lance end to move laterally with arestricted latitude of movement.
 7. A method according to claim 6wherein the latitude of movement of the lance lower end is selected tobe sufficiently great to resist fracture of the lance.
 8. A methodaccording to claim 6 wherein the latitude of movement of the lance lowerend is limited so as to minimize undesirable disturbance of the bath. 9.A method according to claim 7 wherein the lower end of the lance is freeto move through an angle of up to 5.0° from vertical.
 10. A methodaccording to claim 7 wherein the lower end of the lance is free to movethrough an angle of up to 2.5° from vertical.